The invention relates to pressure expansion tanks for closed, hot water systems.
Thermal expansion of heated water may occur wherever water is heated in a closed system (when the water is isolated from the public water supply by a one-way valve: pressure reducing valve, backflow preventer, check valve, etc.). Expansion tanks are designed to absorb thermal expansion and to maintain a predetermined maximum pressure within the closed hot water system. Expansion tanks are used to prevent plumbing system and/or water heater damage and unnecessary relief valve discharge caused by excessive pressure from thermal expansion.
It is known to attach a drum-shaped expansion tank to a closed hot water system, e.g. in a home, to provide a volume for accommodating changes in pressure/volume (often due to changes in water temperature), to resist damage to hot water and heating system components. The tank may include a bladder that moves to vary the available volume in response to changes in pressure.
According to the invention, an in-line expansion tank includes a sleeve defining a volume, a pipe positioned within the sleeve, and an annular flexible bladder disposed within the volume between the sleeve and the pipe. The pipe defines a fluid flow channel with an inlet at an upstream region of the pipe in fluid communication with the fluid flow channel, and an outlet at a downstream region of the pipe in fluid communication with the fluid flow channel. The bladder and the sleeve define an outer radial chamber therebetween.
Embodiments of this aspect of the invention may include one or more of the following features. The radial chamber is pressurized during normal use and the bladder is configured to contact the pipe at normal operating pressure to minimize dead space between the bladder and the pipe. The tank includes a valve for pressurizing the chamber.
In an illustrated embodiment, at the upstream region, the sleeve and bladder are attached to a first end cap, and at the downstream region, the sleeve and bladder are attached to a second end cap. The bladder is attached to the end caps by clamps. O-rings are positioned between the sleeve and the end caps. The first and second end caps each define an inwardly extending lip for retaining the pipe therebetween, and flow channels for allowing fluid communication between the fluid flow channel and a region between the pipe and the bladder.
The tank has an outer diameter of about four inches, and a length in the range of about 24 to 48 inches.
According to another aspect of the invention, a method of accommodating changes in pressure in a piping system includes coupling an inlet of an in-line expansion tank to a first piping system connection, and coupling an outlet of the tank to a second piping system connection in-line with the first connection. The tank includes an outer sleeve, an inner pipe, and an annular, flexible bladder therebetween. The method includes pressurizing a chamber defined between the outer sleeve and the bladder such that the bladder deforms toward an inner pipe under normal operating pressure and expands radially away from the pipe when the pressure in the piping system rises above the normal operating pressure.
The in-line expansion tank of the invention advantageously minimizes dead space between the pipe and the bladder that represents a potential for contamination. The tank is dimensioned to take up less horizontal space than convention drum-shaped expansion tanks.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.